The present invention relates to a novel compound and a silver halide photographic material containing the same. More particularly, the present invention relates to a silver halide photographic material having high sensitivity and less residual color.
A great deal of effort has hitherto been made for increasing the sensitivity of silver halide photographic materials and decreasing residual coloring (residual color) after processing. Sensitizing dyes used for spectral sensitization have been known to have significant influences on the characteristics of silver halide photographic materials. In the sensitizing dyes, the slight differences in structures thereof exert great influences on the photographic characteristics such as sensitivity, fogging and storage stability. However, it is difficult to previously predict the effects thereof, so that many investigators have hitherto made efforts to synthesize a number of sensitizing dyes and to examine the photographic characteristics thereof.
Tabular silver halide grains (hereinafter referred to as tabular grains) have the photographic characteristics that
(1) The ratio of the surface area to the volume is high, which allows a sensitizing dye to be adsorbed on surfaces of the grains in large quantities. As a result, higher color sensitization sensitivity can be obtained;
(2) When an emulsion containing the tabular grains is applied and dried, the grains are arranged on a surface of a support in parallel therewith, which makes it possible to thin the thickness of a coating layer and improve the sharpness;
(3) The tabular grains arranged in parallel with the support maintain their shape and orientation even after development, so that the covering power of developed silver is high. This characteristic can more decrease the amount of silver coated necessary for obtaining the same blackening density, particularly in a roentgen film;
(4) The tabular grains oriented in parallel with the support are decreased in light scattering, so that an image high in resolution can be obtained; and
(5) When the grains are used in a green-sensitive layer or a red-sensitive layer, a yellow filter can be decreased or removed from the emulsion, because of their low sensitivity to blue light.
U.S. Pat. No. 4,439,520 describes a color photographic material in which tabular grains having a thickness of less than 0.3 xcexcm, a diameter of 0.6 xcexcm or more and an aspect ratio of 8 or more are used in at least one layer of a green-sensitive emulsion layer and a red-sensitive emulsion layer, thereby improving the sharpness, the sensitivity and the graininess. The term xe2x80x9caspect ratioxe2x80x9d as used herein means the ratio of the diameter to the thickness of the tabular grain. Further, the term xe2x80x9cdiameter of the tabular grainxe2x80x9d means the diameter of a circle having the same area as the projected area of the grain observed under a microscope or an electron microscope. Furthermore, the thickness is indicated by the distance between two parallel faces constituting the tabular grain.
U.S. Pat. No. 4,693,964 describes a photographic element comprising tabular grains of silver bromide or silver iodobromide having a mean diameter of 0.4 xcexcm to 0.55 xcexcm and an aspect ratio of 8 or more. In this patent, tabular grains having a mean diameter of 0.5 xcexcm and a thickness of 0.04 xcexcm are described in an example. U.S. Pat. No. 4,672,027 describes a photographic element comprising tabular grains of silver bromide or silver iodobromide having a mean diameter of 0.22 xcexcm to 0.55 xcexcm and an aspect ratio of 8 or more. In this patent, tabular grains having a thickness of 0.04 xcexcm are described in an example.
U.S. Pat. No. 5,250,403 describes a color photographic element containing tabular grains having (111) faces as a main plane, a mean diameter of 0.7 xcexcm or more and a mean thickness of less than 0.07 xcexcm in a minus blue (green and/or red) layer. The tabular grains having a mean thickness of less than 0.07 xcexcm are hereinafter referred to as xe2x80x9cextra thinxe2x80x9d tabular grains. This patent describes that an emulsion of the extra thin tabular grains is attractive in the relationship between the sensitivity and the graininess, and that the use in the color photographic element, particularly in the minus blue recording emulsion layer, is advantageous because of the good sharpness of images.
European Patent 362,699 discloses tabular grains having a ratio of the aspect ratio to the diameter of the tabular grain of larger than 0.7. In this patent, the preparation of tabular grains having a thickness of 0.04 xcexcm is described in an example.
Thus, for more highly exhibiting the characteristics of tabular grains, researches have hitherto been centralized on the development of tabular grains having a higher aspect ratio and a thinner thickness. On the other hand, the demand for higher qualities to photographs is strong, and the development of techniques which can attain the higher sensitivity has been desired.
As described above, the tabular grains are high in the ratio of the surface area to the volume, which allows a sensitizing dye to be adsorbed on surfaces of the grains in large quantities, as a result, higher color sensitization sensitivity can be obtained. In that case, in the sensitizing dye, an increase in light absorptivity is considered to improve the transmission efficiency of light energy to the silver halide, thereby attaining an increase in spectral sensitivity.
Thus, the tabular grains are advantageous for obtaining high color sensitization sensitivity. On the other hand, however, the sensitizing dye is adsorbed in large quantities, which introduces the problem that residual color after processing increases.
For the above-mentioned reasons, a sensitizing dye which is high in sensitivity and less in residual color has been desired.
An object of the present invention is to provide a novel compound.
Another object of the present invention is to provide a silver halide light-sensitive material comprising the novel compound, in which generation of fog is decreased, storage stability is excellent and residual color is decreased. As a result of intensive investigation, the objects of the present invention could be attained by the following (1) to (9):
(1) A silver halide photographic material comprising at least one compound represented by the following formula (I): 
xe2x80x83wherein Z1 represents an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, a carbon atom or a nitrogen atom; Q represents a group necessary for forming a methine dye; M1 represents a charge equilibrium counter ion; m1 represents the number necessary for neutralizing a charge of the molecule; VP represents a group having a log P value lower than that of Cl; q1 represents 1, 2, 3 or 4; and R1 is represented by following:
R1=(La)k1CONHSO2R11, R1=(Lb)k2SO2NHCOR12,
R1=(Lc)k3CONHCOR13, R1=(Ld)k4SO2NHSO2R14 
xe2x80x83wherein R11, R12, R13 and R14 each represents an alkyl group, an aryl group, a heterocyclic group, an alkoxyl group, an aryloxy group, a heterocyclyloxy group or an amino group; La, Lb, Lc and Ld each represents a methylene group; and k1, k2, k3 and k4 each represents an integer of 1 to 18;
(2) The silver halide photographic material described in (1), wherein VP is a fluorine atom;
(3) The silver halide photographic material described in (1) or (2), wherein the case that k1 is 2 is excluded;
(4) The silver halide photographic material described in (1), wherein the compound represented by formula (I) is selected from a compound represented by the following formula (II): 
xe2x80x83wherein Z1, R1, M1 and m1 each has the same meaning as given in formula (I); Z2 represents an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, a carbon atom or a nitrogen atom; R2 represents an alkyl group; L1, L2 and L3 each represents a methine group; and n1 represents 0, 1, 2 or 3;
(5) The silver halide photographic material described in (4), wherein the case that k1 in formula (II) is 2 is excluded;
(6) The silver halide photographic material described in (1), wherein the compound represented by formula (I) is selected from a compound represented by the following formula (IIa): 
xe2x80x83wherein M1 and m1 each has the same meaning as given in formula (I); A represents a hydrogen atom, a methyl group, an ethyl group or a propyl group; and R3 is represented by following:
R3=CH2CONHSO2CH3, R3=CH2SO2NHCOCH3,
R3=CH2CONHCOCH3, R3=CH2SO2NHSO2CH3 
(7) The silver halide photographic material described in (1), wherein the compound represented by formula (I) is contained in an emulsion layer comprising silver halide grains having a mean aspect ratio of from 3 to 1,000.
(8) The silver halide photographic material described in (7), wherein the silver halide grains have a mean aspect ratio of from 8 to 100.
(9) A compound represented by formula (I): 
xe2x80x83wherein Z1 represents an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, a carbon atom or a nitrogen atom; Q represents a group necessary for forming a methine dye; M1 represents a charge equilibrium counter ion; ml represents the number necessary for neutralizing a charge of the molecule; VP represents a group having a log P value lower than that of Cl; q1 represents 1, 2, 3 or 4; and R1 is represented by following:
R1=(La)k1CONHSO2R11, R1=(Lb)k2SO2NHCOR12,
R1=(LC)k3CONHCOR13, R1=(Ld)k4SONHSO2R14 
xe2x80x83wherein R11, R12, R13 and R14 each represents an alkyl group, an aryl group, a heterocyclic group, an aryloxy group, a heterocycloxy group or an amino group; La, Lb, Lc and Ld each represents a methylene group; and k1, k2, k3 and k4 each represents an integer of 1 to 18.